After doing so, the fuel pump began making a "whining" noise while running but was especially noticable (annoying!) at start-up and shut-down. At shut-down, my best description would be that the noise was similar to a jet turbine winding down. After several weeks, curiosity led me to place a 5 gallon bucket next to the furnace and convert the pump back to a two-line system to feed from it. QUIET AS A MOUSE, so I bought another roll of tubing and installed it as a return-line to the outside tank, only to find the noise had returned, although in a somewhat different pitch.
Filling the 5 gallon bucket next to the furnace and using it as a "fuel tank" is my short term option but I don't foresee having to do it again next year. Any suggestions would be appreciated!